This is a case of a bunch of people thinking they are so clever they have a story that fits the time. Remember the all-around political conspiracies caught on camera in the years leading to the Watergate and a little later? Most movies trying to cash in on made-for-TV 'o so powerful, o so mind numbing' conspiracies were in fact caught in their own navel-gazing attitude.
I was never a fan of The Conversation which I find as much dated as others conspiracy stints of the time but Coppola was true to his main character and Hackman was a pretty engaging actor to observe. I mean these conspiracy movies are mostly drowning in the character pool of noir heroes. Lots of questions unanswered, lots of dis-communication... Well this takes at least Bergman to build a movie about such un-visual bases.
The Next Man is a perfect example of its time: one political soup served with an idealistic character and an horrendous conspiracy tightening its web around him. Neither part is interesting in itself and the whole doesn't get any better. In fact you can tell how much it will be bad from the very first sequences piling up 'watcha that' murders without ever advancing any storyline. Pedestrian directing at its worst as most of the movie is one pompous accumulation of scenes revolving around violence naively brought under the viewer's eyes.